Treatment of patients with myocardial infarction who present with a paced rhythm

Background: A paced rhythm can mask the electrocardiographic features of an acute myocardial infarction, complicating timely recognition and treatment. Objective: To evaluate characteristics, treatment, and outcomes among patients presenting with paced rhythms during myocardial infarction. Design: Retrospective cohort study. Setting: U.S. acute care hospitals. Patients: 102 249 Medicare beneficiaries at least 65 years of age who were treated for acute myocardial infarction between 1994 and 1996. Measurements: Provision of three treatments for acute myocardial infarction (emergent reperfusion, aspirin, and beta -blockers), death at 30 days, and long-term follow-up. Results: 1954 patients (1.9%) presented with paced rhythms during myocardial infarction. These patients were older; were predominantly male; and had higher rates of congestive heart failure, diabetes, and previous infarction. They were significantly less likely to receive emergent reperfusion (relative risk [RR], 0.27 [95% Cl, 0.22 to 0.33]), aspirin (88 at admission, 0.91 [Cl, 0.88 to 0.94]; RR at discharge, 0.87 [Cl, 0.83 to 0.92]), and beta -blockers at admission (RR, 0.89 [Cl, 0.82 to 0.96]). In addition, there was a trend toward decreased use of beta -blockers at discharge (RR, 0.91 [Cl, 0.76 to 1.06]). Crude mortality rates were higher among patients with paced rhythms than among those without at 30 days (25.8% vs. 21.3%; P = 0.001) and at 1 year (47.1% vs. 36.1%; P = 0.001). Among patients with paced rhythms, risk for death at 30 days decreased after adjustment for illness severity and decreased use of therapy (RR, 1.03 [Cl, 0.93 to 1.14]). Patients with paced rhythms remained at additional risk for long-term mortality (hazard ratio, 1.12 [Cl, 1.06 to 1.18]). Conclusions: Patients with paced rhythms were less likely than those without to receive treatment for acute myocardial infarction and had poorer short- and long-term outcomes. However, this mortality risk diminished after adjustment for treatment This suggests that improved recognition and treatment of myocardial infarction may improve outcomes, particularly in the short term.